The investigation into the poisoning murder of a former KGB spy took a bizarre twist Thursday with reports that a Russian who had tea with Alexander Litvinenko had fallen into a coma, a claim that drew an immediate denial from a lawyer close to the case.

Russian businessman Dmitry Kovtun is a key figure in the investigation into the poisoning of ex-security agent; he met with the former KGB agent at London's Millennium Hotel on Nov. 1, hours before the former spy fell fatally ill.

The Interfax news agency, citing unnamed sources, said Kovtun fell into a coma immediately after being questioned by Russian investigators and Scotland Yard detectives.

But Andrei Romashov, a lawyer for another key figure in the case, told The Associated Press that he contacted Kovtun's representatives after the report and they told him Kovtun's condition was "the same as it was when he met with prosecutors."

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Romashov declined to name Kovtun's representatives.

Interfax news agency reported that British and Russian investigators interrogated Kovtun on Tuesday and Wednesday.

The report from Moscow came on the same day Litvinenko was laid to rest in London, on the heels of a report by the British Health Protection Agency that seven staff members from the hotel's Pine Bar where the pair met former KGB agent Andrei Lugovoi have tested positive for "low levels" of polonium-210, which isn't a short-term health risk and poses little risk to the general public.

Kovtun and Lugovoi have told reporters in Moscow that someone is trying to frame them in Litvinenko's death.

"By the doctors' diagnosis, Kovtun's condition is critical," Interfax quoted the sources as saying. The report could not be immediately confirmed.

British detectives came to Moscow this week to observe the interrogation by Russian authorities of figures linked to the death of Litvinenko, who died in London Nov. 23 of radiation poisoning. One of the first to be questioned was Kovtun, a businessman and former Russian agent who had met with Litvinenko in London on the same day that Litvinenko said he had been poisoned.

Earlier Thursday, Russian prosecutors released a statement saying that Kovtun had "developed an illness also connected with the radioactive nuclide [substance]."

Kovtun had not previously been reported to have fallen ill.

Litvinenko, who reportedly converted to Islam before he died in solidarity with Chechen Muslims, was laid to rest Thursday in a rain-swept funeral at London's Highgate Cemetery.

Self-exiled billionaire Boris Berezovsky, Chechen rebel envoy Akhmed Zakayev and some 50 mourners consoled Litvinenko's widow, Marina, and 12-year-old son, Anatoly, beside his dark oak casket as a steady rain fell.

Lord John Rea, director of the Save Chechnya campaign, held up a picture of crusading Russian journalist Anna Politkovskaya, whose murder the former KGB agent was investigating at the time of his fatal poisoning.

From his deathbed, Litvinenko blamed his fate on Russian President Vladimir Putin — a charge that Kremlin officials have called "nonsense." Traces of highly radioactive polonium-210 were found in Litvinenko's body after his Nov. 23 death.

Scotland Yard on Wednesday said it was investigating his death as a homicide, and traces of radiation have been found at more than a dozen sites in Britain and on jetliners that flew between London and Moscow.

Prosecutors in Moscow said they had also opened a criminal case into Litvinenko's death, allowing suspects to be prosecuted in Russia. Officials there previously have said that Russia would not allow the extradition of any suspects in Litvinenko's death.

Litvinenko, who also criticized Putin's policies in Chechnya, reportedly had converted to Islam before his death, and some of the mourners were dressed in traditional Muslim robes. They left red flowers and an orange and yellow wreath at the stone gate of the famous cemetery where communist revolutionary Karl Marx is buried.

Earlier Thursday, Zakayev and Litvinenko's father, Walter, joined hundreds of Muslims who had gathered at London's Regent's Park Mosque for regular daily prayer to attend a memorial service, where the imam recited a funeral prayer.

"The imam said a special passage for him from the Koran," said Ghayasuddin Siddiqui, head of Britain's Muslim parliament.

Walter Litvinenko and Zakayev both insisted the former spy had converted to Islam on his deathbed, although some friends disputed the claim — saying he had merely expressed empathy with Chechen Muslims. Siddiqui said the mosque had been told Litvinenko converted to Islam 10 days before he was admitted to a hospital last month.

Vladimir Bukovsky, a friend and fellow Putin critic, said Litvinenko had asked that his body eventually be moved to Chechnya. The region in southern Russia is mostly Muslim and plagued by rebel attacks as well as violence blamed on federal troops and forces of the Moscow-backed Chechen government.

"On his deathbed, he asked to be buried when the war is over in Chechen soil," Bukovsky said. "He was a fierce defender of Chechnya and critic of the Kremlin."

As investigations proceeded in both London and Moscow, a scheduled interview with former KGB agent Andrei Lugovoi, who met Litvinenko the day he fell ill and is regarded as a key witness, was postponed, Lugovoi's lawyer told The Associated Press. Lugovoi said he would answer all the British investigators' questions, the ITAR-Tass news agency reported.

The Russian Prosecutor General's office also said it had opened a criminal investigation into the attempted killing of Kovtun, who, along with Lugovoi, met Litvinenko on Nov. 1 in London.

Lugovoi was at one point a bodyguard for former Russian Prime Minister Yegor Gaidar, who also fell sick recently in Ireland with an illness that Russian doctors have been unable to diagnose. On Thursday, Britain's Financial Times and the Russian newspaper Vedomosti published a letter written by Gaidar with the headline: "I was poisoned and Russia's political enemies were surely behind it."

"Most likely ... some obvious or hidden adversaries of the Russian authorities stand behind the scenes of this event, those who are interested in further radical deterioration of relations between Russia and the West," Gaidar wrote in the letter.

Faint levels of polonium-210 had been found at two locations at London's Emirates Stadium, where Lugovoi and Kovtun attended a soccer match Nov. 1, officials said Wednesday.

The radiation was "barely detectable" and posed no public health risk, government health agency spokeswoman Katherine Lewis said.

Traces also were found at the British Embassy in Moscow, the Foreign Office said. Officials said the level was low and posed no risk to health.

Lugovoi is now hospitalized in Moscow for tests for possible radiation contamination. Kovtun, who had not previously been reported to have fallen ill, developed an illness connected with polonium-210, Russian authorities said.

Litvinenko's father told Radio Free Europe on Wednesday that his son had said he had converted to Islam two days before his death. Several friends also said the former agent had converted.

"It was a deeply personal thing, the result of a very intimate personal process, and there's absolutely no connection to his political views," said a Russian friend, who requested anonymity because of the sensitivity of the issue.

He said the Litvinenko family had decided to hold a nonreligious burial because they feared an "inevitable attempt by Litvinenko's enemies to portray him as an associate of Islamist extremists."

Zakayev said that on the day before Litvinenko died, the former spy was visited in hospital by an imam, who read a Koranic verse traditionally said over the dying.

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The Associated Press contributed to this report.